Low resistivity copper germanide on (100)Si for contacts and interconnections

We have deposited thin films of Cu3Ge on (100) Si by the sequential e-beam deposition of an amorphous Ge layer followed by a polycrystalline Cu layer. The films were then annealed in flowing N-2 for 30 min over a temperature range of 150-600 degrees C to induce complete recrystallization of the Cu-Ge films. Films of Cu3Ge form a smooth, atomically sharp interface with (100) Si over a wide range of anneal temperatures, as determined by transmission electron microscopy, indicating the lack of any chemical reactions, i.e., compound formation, at the film/substrate interface. We have observed by secondary ion mass spectrometry, that a substantial amount of Si has diffused into the Cu-Ge in varying amounts that exhibit strong dependence on the anneal temperature. Despite the large amount of Si that has diffused into the films, the Cu3Ge maintains its low resistivity (rho=10-15 mu Omega cm) up to an anneal temperature of 600 degrees C, at which point the film completely loses its structural integrity, i.e., it becomes discontinuous with the formation of complex compounds. These results show that Cu3Ge represents a potential candidate material for contact and metallization for next generation Si-based semiconductor devices. (C) 1996 American Institute of Physics.